This invention relates to parallel access magnetic bubble memory systems and more particularly to such systems employing integrated optics techniques for bubble detection.
Substantial advances have been made in many areas of cylindrical domain or magnetic bubble technology, but one of the significant problems remaining is that of accessing bubble memories by providing a readout. Various types of detectors have been developed for reading or detecting magnetic bubbles as they are moved along a predetermined path and past a read position of a magnetic domain memory. These detectors provide a discrete output signal indicative of the passage of a bubble by the read position. The majority of such detection systems have utilized various magneto-resistive elements, usually formed of a pattern of magnetically soft overlay material, to electrically sense the flux field of the bubble and thereby provide an electrical signal. Such detectors may be satisfactorily fabricated and provide a generally acceptable signal-to-noise ratio, but it would be desirable to be able to provide a detector with an enhanced signal-to-noise ratio. Moreover, these detectors require electronic detector elements and their leads to be placed on the memory chip, all of which diminishes the space available for memory storage on the chip. Prior magnetic bubble memory systems have typically utilized major/minor loop organizations with a single detector used for serially accessing bubbles moved from the minor loops onto the major loop.
The presence of magnetic bubbles in typical magnetic-bubble garnet layers has also been sensed or detected optically but, because of the precise alignment requirements of the optics relative to the detection area and the difficulty in economically fabricating such optical arrangements, progress has been slow in this area and optical methods have hitherto appeared unsuitable in a practical sense.